Stylus actuated gas discharge system

ABSTRACT

A DISPLAY SYSTEM INCLUDING A GAS DISCHARGE DISPLAY PANEL MADE UP OF AN ASSEMBLY OF GLASS FILMS ENCLOSING A GAS AND INCLUDING ELECTRODES THAT DEFINE AN ARRAY OF DISCRETE CELLS. A SOURCE OF SUSTAINING VOLTAGE IS APPLIED TO THE ELECTRODES TO MAINTAIN THE GAS SLIGHTLY BELOW A THRESHOLD VALUE. A HAND STYLUS WHICH PRODUCES A HIGH VOLTAGE DISCHARGE IS CONNECTED TO THE SOURCE OF SUSTAIN-   ING VOLTAGE AND IS EMPLOYED TO SELECTIVELY EXCITE THE CELLS WHICH THEN EMIT VISIBLE LIGHT SELECTIVELY EXTINGUISHED.

I 1 Feb. 12," 1971 v I Filed mayzs, 1959 2 Sheets-Sheet 1 FIG. 2

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': Filed may 26,- 19,69

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FIG. 4

United States Patent STYLUS ACTUATED GAS DISCHARGE SYSTEM Enval S.Barrekette, New York, and Herbert B. Baskin,

Mohegan Lake, N.Y., assignors to International Business MachinesCorporation, Armonk, N.Y., a corporation of New York Filed May 26, 1969,Ser. No. 827,598 Int. Cl. B431 1/00 US. C]. 35-61 9 Claims ABSTRACT OFTHE DISCLOSURE A display system including a gas discharge display panelmade up of an assembly of glass films enclosing a gas and includingelectrodes that define an array of discrete cells. A source ofsustaining voltage is applied to the electrodes to maintain the gasslightly below a threshold value. A hand held stylus which produces ahigh voltage discharge is connected to the source of sustaining voltageand is employed to selectively excite the cells which then emit visiblelight until selectively extinguished.

BACKGROUND OF THE INVENTION Field of the invention The present inventionis in the field of gas discharge display panels.

Prior art Gas discharge display panels of the type employed in thepresent invention are described in the article, Plasma Display PanelsReviewed at WESCON, page 8, EDN Sept. 16, 1968, vol. l3, No. 18. Thedescribed panel is distinct from the present invention in that it isactuated by computer generated signals connected to the electrodes. Theprior art displays do not have the feature of providing human inteactionwith a stylus.

SUMMARY OF THE INVENTION Heretofore, display panels of the gas dischargetype have been actuated by signals connected directly to the electrodes.They display includes a matrix of thousands of small separate cells. Alogic system is required to convert a desired display or pattern intoproper input signals to actuate the proper ones of the large number ofcells.

An object of the present invention is to provide a system for generatingpatterns on a gas discharge display panel in real time without requiringlogic circuits.

Another object of the present invention is to provide a system forgenerating patterns on a gas discharge display panel by a human operatorusing a stylus.

A further object of the present invention is to provide a system whereina human operator and a computer can interact through a gas dischargedisplay panel.

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of the preferred embodiments of the invention, asillustrated in the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a schematic block diagram of an embodiment of a gas dischargedisplay panel system following the principles of the present invention.

FIG. 2 is an illustration of waveforms useful in explaining theembodiment of FIG. 1.

FIG. 3 is an illustration of another embodiment of a stylus which may beused in the present invention.

FIG. 4 is a schematic block diagram of an embodiment of the presentinvention employing a data processing system.

DESCRIPTION OF THE PREFERRED 5 EMBODIMENTS Referring to FIG. 1, a gasdischarge display panel system is shown including a gas dischargedisplay panel 10, a source of sustaining signal 12, a high voltagedischarge stylus 14 with its associated voltage source 16 and connectingcircuit 18 between stylus 14 and sustaining signal source 12.

Display panel is a known device. It is described in the reference citedin the preceding Prior Art paragraph. The panel includes two glassplates, one containmg a plurality of transparent conductors extending inthe X direction and the other a plurality of conductors ex tending inthe Y direction. In one type of display panel, the two glass plates formone large gas chamber With the X conductors on one side and the Yconductors on the other side forming a plurality of matrix intersectionpoints. In another type of display panel, the two glass panels whichform the plurality of matrix points are separated by an intermediatethird glass panel having holes at the intersection points to form aplurality of separate cells which are filled with a gas, for example,neon or a helium-neon mixture. In either case, the region of gas excitedinto the visible state at an intersection point will be hereinafterreferred to as a cell.

A sinusoidal sustaining voltage from generator 12 is applied to the Xand Y conductors to excite the gas in the cells to a value below thethreshold value at which discharge occurs. Thus, a potential isestablished across the gas in the intersection regions (i.e., in each ofthe cells) of the display device 10.

Stylus 14 contains an induction coil which produces a high voltage, lowcurrent, high frequency (R.F.) discharge. An example of a coil of thistype is a Tesla coil which is described in the International Dictionaryof Physics and Electronics, copyright 1956 by D. Van Nostrand Company,Inc., Princeton, NJ. Stylus 14 is placed on the desired location ofdisplay panel 10 and the voltage discharge produced by stylus 14 issufficient to further excite the gas in the cell proximate to stylus 14to produce visible light. When the gas is excited into the visiblestate, ions transfer across the intersection point from one conductor tothe other to maintain the gas in the visible state when the voltagedischarge produced by stylus 14 is removed. The gas will stay visibleuntil an erase signal is provided by stylus 14.

More particularly, sustaining generator 12 produces a sinusoidalsustaining voltage as depicted as waveform A of FIG. 2. The sustainingsignal is applied to a differentiating circuit 18 which differentiatesthe signal to produce a signal having a waveform shown as waveform B ofFIG. 2. The positive and negative voltage spikes of waveform B occursimultaneously with the peaks of the sustaining signal applied todisplay panel 10.

The output signal from differentiating circuit 20 is applied to twoclipping circuits 22 and 24. Clipping circuit 22 clips the waveform Bsignal of FIG. 2 to produce an output signal including only the positivespikes as shown as Waveform C of FIG. 2. Clipping circuit 24 clips thewaveform B signal to produce an output signal consisting only of thenegative spikes as shown as waveform E of FIG. 2. The output signal fromclipping circuit 24 is applied to an inverting circuit 26 which invertsthe polarity of the negative spikes to produce an output signalconsisting of positive spikes. Thus, the output signal from clippingcircuit 22 is a series of positive voltage spikes concurrent in timewith the positive peaks of the sustaining signal shown as waveform A.The output signal from inverting circuit 26 consists of a series ofpositive voltage spikes concurrent in time with the negative peaks ofthe sustaining signal. The supply voltage for stylus 14 from voltagesource 16 is applied to an AND circuit 28 along with the output signalfrom inverting circuit 26 and also to an AND circuit 30 along with theoutput signal from clipping circuit 22. AND circuit 30, therefore,produces an output voltage signal concurrent in time with the positivepeaks of the sustaining signal and an AND circuit 28 produces an outputvoltage signal concurrent with the negative peaks of the sustainingsignal. The output signal from AND circuit 30 is applied to a gatecircuit inside the stylus 14 which is controlled by button 32 and theoutput from AND circuit 28 is applied to another gate circuit insidestylus 14 which is controlled by button 34. Thus, when button 32 isdepressed, stylus 14 will produce a high voltage discharge upon the nextoccurrence of a positive peak of the sustaining signal. When button 34is depressed, stylus 14 will produce a high voltage discharge upon thenext occurrence of a negative peak of the sustaining signal. Button 32is depressed when it is desired to write on the display panel and button34 is depressed when it is desired to erase the display panel. The writebutton 32 may be replaced by a pressure operated plunger in the tip oftylus 14 which is brought into contact with the face of display panel 10when a write operation is desired. Alternatively, the erase button 34may be replaced by the pressure operated plunger.

Referring to waveform E of FIG. 2, a signal is shown illustrating thecooperation of the output signal of stylus '14 and the sustaining signalfrom sustaining generator 12. Sometime after the occurrence of thesecond positive peak of the sustaining signal, the write button 32 ofstylus 14 is depressed thereby opening the associated gate andpermitting stylus 14 to operate. At the time of the next positive peak(the third peak) of the sustaining signal, a voltage discharge isproduced by stylus 14 and directed to a desired cell of display panel10. The voltage discharge from stylus 14 adds to the positive peak ofthe sustaining signal at the desired cell as shown in waveform E and issufiicient to exceed the threshold value required to excite the gas inthe cell into the visible state. The cell will stay visible after theoccurrence of the voltage discharge from stylus 14 and the release ofbutton 32. Presuming that the erase button 34 is depressed after theoccurrence of the third negative peak of the sustaining signal, avoltage discharge will be produced from stylus 14 upon the occurrence ofthe next or fourth negative peak of the sustaining signal. A positivevoltage discharge from stylus 14 subtracts from the negative peak of thesustaining signal. The negative voltage is no longer suflicient tomaintain the ion flow necessary to maintaln the gas in the visible stateand the gas returns to its original unexcited below threshold level andthe gas in the cell is no longer visible.

What has been described is a gas discharge display panel wherein the gasin the individual cells can be made selectively visible under thecontrol of an operator in real time by the use of a hand held stylus. Asthe operator moves the probe in desired patterns across the face of thedisplay panel, a corresponding illuminated pattern w1ll be produced onthe face of the display panel.

FIG. 1 illustrated an embodiment of the invention wherein the probe 14was synchronized with the sustaining signal. A stylus 14A is shown whichmay be employed with a different embodiment. The stylus is connected tovoltage source 16. In between the high voltage coils (not shown) andvoltage 16, a write button is connected which, when depressed, connectsthe voltage coils to the voltage source to produce a discharge whichwill make the gas visible upon the occurrence of the next posltive peakof the sustaining signal. Button 38 must be released or stylus 14A movedprior to the negative peak of the sustaining signal or erasure willoccur.

The tip of stylus 14A contains a photodiode 40 which provides almostinfinite resistance when dark and almost zero resistance whenilluminated. Photodiode 40' is shielded during the writing operation.When erasing is desired, the light from the display cell will causephotodiode to operate as a switch, thereby connecting voltage source 16to the voltage coils. The stylus thus produces a discharge which willerase the lighted cell on the occurrence of the next negative peak ofthe sustaining signal.

If the sustaining signal has a relatively low frequency, for example,sixty cycles per second, a simple stylus having a single on-otf buttoncan be used.

It is also possible to provide a stylus which produces a positive writevoltage discharge and a negative erase discharge, both of which operateon the positive peaks of the sustaining signal.

In another system embodiment, a stylus can be used with a display panelwhich is also connected to a computer. This type system has theadvantage that the operator can interact with the computer. Referring toFIG. 4, a system is shown combining a computer operated display panelknown in the prior art with a high voltage discharge stylus to provideinteraction not obtainable with prior art systems. Elements of thesystem of FIG. 4 which are the same as elements of FIG. 1 are designatedwith the same reference numbers.

The system of FIG. 4 includes a gas discharge display panel 10 and asustaining generator 12. Sustaining generator 12 is connected throughcircuit 18 to stylus 14. Buttons 32 and 34 of stylus 14 functionidentically as described relative to FIG. 1. Circuit 18 includesdifferentiating circuit 20, clipping circuits 22 and 24, invertingcircuit 26 and AND circuits 28 and 30 which function identically totheir counterparts in FIG. 1.

Rather than being connected directly to display panel 10, sustaininggenerator 12 is connected to X pulser 44 and Y pulser 46. A computer 48containing the programmed information for the display panel 10 isconnected to address logic circuit 50 which converts the computerinformation into X and Y input signal information. The output of theaddress logic circuit 50 is connected to X pulser 44 and Y pulser 46which apply pulses on the sustaining signal from generator 12 in amanner illustrated in waveform E of FIG. 2 to provide write pulses anderase pulses. X pulser 44 and Y pulser 46 are connected individually toeach of the X conductors and Y conductors of display panel 10 and, undercontrol of computer 48 and address logic 50, apply either write pulsesor erase pulses to the appropriate X and Y conductors of display panel10 to efiect a desired gas cell in the panel 10. As previously stated,this is how prior art gas display panels are operated.

The sustaining signal from generator 12 is also connected throughdifferentiating circuit 20, clipping circuits 22 and 24, invertingcircuit 26 and AND circuits 28 and 30 to stylus 15 along with thevoltage from voltage source 16. The write button 32 and the erase button34 of stylus 14 can therefore be actuated by an operator in a mannerdescribed relative to FIG. 1 to add to or erase from the displayproduced by computer 48. In order that computer 48 can obtain theinformation introduced by the operator, the X conductors and the Yconductors of display panel 10 are connected to sensing circuits 53 and55 via cables 52 and 54 respectively. The outputs of sensing circuits 53and 55 are connected to computer 48. When the operator either writes orerases a given gas cell of display panel 10, a corresponding change involtage level occurs on the X conductor and Y conductor associated withthe gas cell. This voltage level change is transmitted on thecorresponding leads in cables 52 and 54 to the sensing circuits 53 and54 which produce output signals in response to the voltage level change.The output signals from sensing circuit 53 and 55 are connected to aregister or core storage in computer 48 to indicate that the operatorhas written or erased a gas cell.

Another form of operator-computer interaction action which is desirableis selection. For example, in computer assisted instruction applicationscomputer 48 may display a question and a number of possible answers. Theoperator then selects the one answer. Thus, to inform computer 48 of aselection, the operator positions stylus 14 next to the selected answerand depresses and holds down both buttons 32 and 34. This maintains thegates in stylus 14 open and generates a sequence of write and erasepulses which are directed at one gas cell. The fact that one cell isbeing continuously written and erased is manifested by 1 alternatevoltage level changes on the appropriate conductors in cables 52 and 54which are applied to sensing circuits 53 and 55 which applycorresponding signals to computer 48.

While the invention has been particularly shown and described withreference to preferred embodiments thereof, it will be understood bythose skilled in the art that various changes in form and details may bemade therein without departing from the spirit and scope of theinvention.

What is claimed is:

1. A gas discharge display system comprising:

a display panel including first and second plates connected together toform a central chamber containing gas,

a first plurality of electrical conductors located on said first plateand a second plurality of electrical conductors located on said secondplate to form intersection regions with said first plurality conductors,

a source of sustaining voltage signal connected to said first and secondplurality of conductors to apply a voltage level to said gas in saidintersection regions between said first and second plurality ofconductors,

and a discharge voltage source for producing a voltage dischargeproximate to the gas in selected intersection regions of said displaypanel.

2. A gas discharge display system according to claim 1 wherein saiddischarge voltage source includes a voltage supply source and a styluscontaining a voltage discharge coil connected to said voltage supplysource for producing a voltage discharge proximate to an intersectionregion of said display panel.

3. A gas discharge display system according to claim 1 wherein saiddischarge voltage produced by said discharge voltage source excites thegas in said intersection region into the Visible state.

4. A gas discharge display system according to claim 3 wherein saiddischarge voltage source produces a voltage discharge proximate to anintersection region of said dislay panel having gas in the visible stateto render said gas in said intersection region nonvisible.

5. A gas discharge display system according to claim 1 further includingmeans connected to said source of sustaining voltage signal and to eachone of said first and second plurality of conductors for producingvoltage pulses on selected ones of said first and second plurality ofconductors for exciting the gas in the intersection regions associatedwith said conductors into the visible state.

6. A gas discharge display system according to claim 4 wherein saidsustaining voltage signal is an alternating current signal and whereinsaid voltage alternates between first and second voltage peak levels,

and wherein said voltage discharge coil in said stylus produces avoltage discharge to excite said gas in said intersection regions intothe visible state concurrent with said first peak voltage level of saidsustaining signal and wherein said voltage discharge coil in said stylusproduces a voltage discharge to render said gas in said intersectionregions nonvisible con- 5 current with said second peak voltage level ofsaid sustaining signal. 7. A gas discharge display system according toclaim 6 including a differentiating circuit connected to said sustainingvoltage signal source for producing voltage pulses on a first outputlead in response to the occurrence of said first peak levels of saidsustaining voltage and voltage pulses on a second output lead inresponse to the occurrence of said second peak levels of said sustainingvoltage, first gating means connected to said stylus, said voltagesupply source and said first output lead for gating said voltage supplyvoltage to said stylus upon the occurrences of the voltage pulses onsaid first output lead,

second gating means connected to said stylus, said voltage supply sourceand said second output lead for gating said voltage supply voltage tosaid stylus upon the occurrences of the voltage pulses on said secondsupply lead,

the output of said first gating means being connected to a first switchin said stylus for selectively applying said gated voltage supplyvoltage to said voltage discharge coil of said stylus,

and the output of said second gating means being connected to a secondswitch in said stylus for selectively applying said gated voltage supplyvoltage to said .voltage discharge coil of said stylus.

8. A gas discharge display system according to claim 7 wherein saidsecond switch in said stylus is a light response switch located in thetip of said stylus.

9. A gas discharge display system according to claim 7 35 furtherincluding a data processing means connected to said sustaining voltagesignal source and to each one of said first and second plurality ofconductors for generating and applying voltage pulses on selected onesof said first and second plurality of conductors for exciting the 40 gasin the intersection regions associated with said conductors into thevisible state,

and means connecting each of said first and second plurality ofconductors to said data processing means for transmitting signal changesto said data processing OTHER REFERENCES Plasma display panels reviewedat WESCON, p. 8,

60 EDN, Sept. 16, 1968, vol. 13, No. 18.

HARLAND S. SKOGQUIST, Primary Examiner US. Cl. X.R.

Disclaimer 3,559,307.-Euval S. Barrekette, New York, and Herbert B.Baskin, Mohegan Lake, N.Y. STYLUS ACTUATED GAS DISCHARGE SYSTEM. Patentdated Feb. 2, 1971. Disclaimer filed Dec. 17, 1973, by the assignee,International Business M (whim Corporation. Hereby enters thisdisclaimer to claims 19, inclusive, of said patent.

[Oflicz'al Gazette April 16, 1974.]

